System for sealing piston rod in cylinder comprises annular seal and sealing ring system enclosing expandable tube filled with pressurizing medium, extra medium being added through cannula with cutting tip

摘要

The system for sealing a piston rod (11) or piston in a cylinder (12) comprises an annular seal (20) and a sealing ring system (22, 24) mounted in a recess in the cylinder. The inner sealing ring encloses an expandable tubular ring (23) filled with pressurizing medium. The ring can be expanded to compensate for slipping of the sealing rings by introducing additional pressurizing medium through a cannula (25). This has a cutting tip (50) which cuts through the inner wall of the tube.